The 'ghost' that you meet when you go to school.A character that comes out of your imagination,and is a criminal to your parents,because he or she took the family money that you were making when developing your hobbies and interests.

1) the opposite of who you usually are and your presonality (e.g. a hippie's alter ego would be a fascist dictator)
2. the bad side of a person that may come to life at anytime, switching your personality (this is fantasy, though some people may believe they have an alter-ego in which they can't control).
3) A person who you aren't ut you act as sometimes as though you have transformed (e.g Eminem's alter ego is Slim Shady)

The dramatic change of personality some people undergo after consuming ecxtasy or other narcotics. They have no recollection of taking on there embarrasing alter-E-go or anything they do when they've changed.

Friend 1: "no way is that Anton rolling around on the dancefloor naked?".
Friend 2: "no man that's Bernard his alter-E-go!".